Heat pipe

ABSTRACT

A heat pipe has a tube and an evaporator wick. The tube has multiple groove structures, an evaporator section, and a condenser section. The groove structures are disposed on an inner surface of the tube and extend to two opposite ends of the tube to reduce flow resistance of liquid phase working fluid. The evaporator wick is disposed in the evaporator section. The evaporator wick is made of metal powder and sintered to adhere to the groove structures. The evaporator wick is uniform in thickness and uniformly adheres to the groove structures. The evaporator wick vaporizes the working fluid in the evaporator section. As a result, the heat pipe has good manufacturing process repeatability and is reliable, easy to manufacture, and low-cost.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a heat-transfer component, especially to a heat pipe.

2. Description of the Prior Arts

Heat pipe is a hollow metal tube sealed at both ends. A working fluid is contained in a sealed chamber of the metal tube. The heat pipe further has a capillary structure formed in the sealed chamber. Mechanism of the heat pipe is described as follows. Liquid-phase working fluid vaporizes into gas-phase working fluid by absorbing heat in an evaporator section and results in localized high pressure in the sealed chamber. Then, the gas-phase working fluid is driven by the localized high pressure to travel toward a condenser section at a high speed. The gas-phase working fluid is cooled down and condenses into liquid-phase working fluid in the condenser section. Then, the condensed working fluid travels back to the evaporator section via the capillary structure to complete a closed loop. That is, via cyclic liquid-vapor phase transition of the working fluid inside the sealed chamber, the heat pipe is capable of balancing temperature promptly to transfer heat.

The heat pipe has a wide range of applications. Applications of the heat pipe start from the aerospace industry, but now the heat pipe has been widely used in all kinds of heat exchangers and coolers. Moreover, the heat pipe has become the most commonly used high efficient heat transfer component in heat dissipation devices for electronics. Heat transfer rate of the heat pipe urgently needs to be improved as heat flux increases rapidly and heat dissipation space reduces. At a fixed size of the heat pipe and a fixed type of the working fluid, the heat transfer rate of the heat pipe is determined by the capillary structure. As a result, the present invention aims at improving the capillary structure and optimizing position of the capillary structure to increase heat transfer rate.

SUMMARY OF THE INVENTION

The main objective of the present invention is to provide a heat pipe with higher heat transfer rate.

The heat pipe of a first configuration has a tube, two end-caps, and an evaporator wick. The tube has multiple groove structures, an evaporator section, and a condenser section. The groove structures are disposed on an inner surface of the tube and arranged along a circumference of the tube. Each one of the groove structures extends along an axial direction of the tube and extends to two opposite ends of the tube. Each one of the two end-caps is disposed at a respective one of the two opposite ends of the tube. The two end-caps seal the tube. The evaporator wick is disposed in the evaporator section. The evaporator wick is made of metal powder and is sintered to adhere to the groove structures. The evaporator wick is substantially uniform in thickness and uniformly adheres to the groove structures. The evaporator wick vaporizes a working fluid in the evaporator section.

The heat pipe of a second configuration has a tube and an evaporator wick. The tube has multiple groove structures, an evaporator section, and a condenser section. The groove structures are disposed on an inner surface of the tube and arranged along a circumference of the tube. Each one of the groove structures extends along an axial direction of the tube and extends to two opposite ends of the tube to reduce flow resistance of liquid phase working fluid. The evaporator wick is disposed in the evaporator section. The evaporator wick is made of metal powder and is sintered to adhere to the groove structures. The evaporator wick is substantially uniform in thickness and uniformly adheres to the groove structures. The evaporator wick vaporizes the working fluid in the evaporator section.

The heat pipe has the following advantages in comparison to a conventional heat pipe: the present invention provides the heat pipe having groove structures formed in the inner surface of the tube and disposed in the evaporator section to provide a large surface area for vaporization for the working fluid infiltrating in the evaporator wick and increases capillary force of the evaporator wick. A second condenser wick is made of metal powder or mesh, and therefore has a very small capability radius r_(eff) which provides a strong capillary force. The groove structures have high permeability K to reduce flow resistance of returning liquid-phase working fluid, which enables the condensed liquid-phase working fluid to quickly return to the whole evaporator section. The present invention has a high capillary force and a high permeability K at the same time to improve heat transfer rate of the heat pipe, solving a dilemma of the conventional single type capillary structure. The present invention has good manufacturing process repeatability and is reliable, easy to manufacture, and low-cost.

Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a first embodiment of a heat pipe in accordance with the present invention;

FIG. 2 is a sectional view of the heat pipe along line 2-2 in FIG. 1;

FIG. 3 is a sectional view of the heat pipe along line 3-3 in FIG. 1;

FIG. 4 is a sectional view of a second embodiment of a heat pipe in accordance with the present invention;

FIG. 5 is a sectional view of the heat pipe along line 5-5 in FIG. 4;

FIG. 6 is a sectional view of the heat pipe along line 6-6 in FIG. 4;

FIG. 7 is a sectional view of a third embodiment of a heat pipe in accordance with the present invention;

FIG. 8 is a sectional view of the heat pipe along line 8-8 in FIG. 7;

FIG. 9 is a sectional view of the heat pipe along line 9-9 in FIG. 7;

FIG. 10 is a sectional view of the heat pipe along line 10-10 in FIG. 7;

FIG. 11 is a sectional view of a fourth embodiment of a heat pipe in accordance with the present invention:

FIG. 12 is a sectional view of the heat pipe along line 12-12 in FIG. 11;

FIG. 13 is a sectional view of the heat pipe along line 13-13 in FIG. 11;

FIG. 14 is a sectional view of a fifth embodiment of a heat pipe in accordance with the present invention;

FIG. 15 is a sectional view of the heat pipe along line 15-15 in FIG. 14; and

FIG. 16 is a sectional view of the heat pipe along line 16-16 in FIG. 14.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention improves and optimizes structure of the heat pipe on the basic principle of heat transfer rate of heat pipe to improve heat transfer rate of the heat pipe.

Maximum heat transfer rate of the heat pipe is hereby defined as Q_(max), which can be calculated using the following function:

$Q_{\max} = {2 \times \frac{\rho \cdot h_{fg} \cdot \sigma}{\mu} \times \frac{A_{w}}{L_{eff}} \times \frac{{K \cdot \cos}\theta_{e}}{r_{eff}}}$

wherein:

$\frac{\rho \cdot h_{fg} \cdot \sigma}{\mu}$

stands for liquid property of the working fluid, wherein ρ is liquid density, h_(fg) is latent heat of vaporization, and σ is liquid viscosity.

$\frac{A_{w}}{L_{eff}}$

stands for dimensions of heat pipe, wherein A_(w) is sectional area of the heat pipe, and L_(eff) is effective length of the heat pipe.

$\frac{{K \cdot \cos}\theta_{e}}{r_{eff}}$

stands for capillary structure property, wherein K is permeability, r_(eff) is capability radius, and θ_(e) is contact angle.

From the above function, one can induce that for the heat pipe with fixed dimensions and working fluid, the heat transfer rate is determined by the capillary structure. The heat transfer rate increases as the permeability K increases and as the capability radius r_(eff) decreases. As a result, the present invention mainly focuses on researching permeability K and capability radius r_(eff).

Common capillary structures used in heat pipes include groove type, sintered type, and mesh type. When selecting the capillary structure, from the perspective of providing maximum heat transfer rate, the capillary structure should have very small capability radius r_(eff) which provides a sufficiently large capability force, and the capillary structure should have a higher permeability K to reduce flow resistance of returning liquid.

Single type capillary structure can hardly have a high capillary force and a high permeability K at the same time. The groove type capillary structure utilizes concave meniscus of the working fluid to generate capillary force. Although the capillary force of the groove type capillary structure is smaller, the capillary structure has larger permeability K to reduce flow resistance of returning liquid. As a result, the groove type capillary structure can achieve higher axial heat transfer rate.

The sintered type and the mesh type capillary structures generate larger capillary force due to smaller capability radiusr_(eff), and therefore transfer larger amount of heat. However, smaller permeability K results in larger flow resistance of returning liquid, and larger capillary force also increases larger flow resistance of returning liquid.

The present invention provides a heat pipe with composite capillary structure that provides a high capillary force and a high permeability at the same time such that the heat transfer rate of the heat pipe can be improved through higher capillary force and higher axial heat transfer rate. The capillary structure is divided into an evaporator wick and groove structures. Although the capillary force of the groove structures are smaller, the groove structures have larger permeability K to reduce flow resistance, thereby having higher axial fluid transfer capability. Therefore, the evaporator wick is plentifully supplied with working fluid, and the heat transfer rate of the heat pipe is improved.

First Embodiment

With reference to FIGS. 1 to 3, FIG. 1 is a sectional view of the first embodiment of a heat pipe 10 in accordance with the present invention. FIG. 2 is a sectional view of the heat pipe 10 in FIG. 1, showing the heat pipe 10 cut across a cutting plane line 2-2 in FIG. 1. FIG. 3 is a sectional view of the heat pipe 10 in FIG. 1, showing the heat pipe 10 cut across a cutting plane line 3-3 in FIG. 1.

The heat pipe 10 has a tube 100, an evaporator end-cap 200, a condenser end-cap 300, and an evaporator wick 400. Multiple groove structures 101 are disposed on an inner surface of the tube 100 and arranged along a circumference of the tube 100. Each one of the groove structures 101 extends along an axial direction of the tube 100 and extends to two opposite ends of the tube 100. In other words, the groove structures 101 are disposed along the axial direction of the tube 100 and extend transversely across the whole inner surface of the tube 100 along a lengthwise direction of the tube 100.

The groove structures 101 are integrally formed in the tube 100. The groove structures 101 are preferably evenly arranged along the circumference of the tube 100, which means the groove structures 101 are evenly arranged along a 360 degree area around a center of the tube 100, but the groove structures 101 are not limited thereto. In another preferred embodiment, for areas of the tube 100 that are not in contact with heating blocks or cooling fins, density of the groove structures 101 can be lower, or there can be no groove structures 101 in said areas.

An evaporator section 110 and a condenser section 120 are disposed on the tube 100. To be precise, the evaporator section 110 and the condenser section 120 are independent from each other and are arranged along the axial direction of the tube 100. The evaporator end-cap 200 and the condenser end-cap 300 are each disposed at a respective one of the two opposite ends of the tube 100 to seal the tube 100.

The evaporator wick 400 is disposed in the evaporator section 110. The evaporator wick 400 is made of metal powder and sintered to adhere to the groove structures 101. The evaporator wick 400 is substantially uniform in thickness and uniformly adhering to the groove structures 101. The evaporator wick 400 vaporizes a working fluid in the evaporator section 110 into vapor. The groove structures 101 extend to the condenser section 120 to return condensed liquid-phase working fluid from the condenser section 120 to the evaporator section 110.

Flow directions of working fluid vapor are indicated by dashed lines with arrows in FIG. 1. Working process of the heat pipe 10 is as below. The evaporator section 110 absorbs heat from a heat source and vaporizes working fluid into vapor, resulting in localized high pressure which drives the vapor to flow toward the condenser section 120. The vapor condenses into liquid in the condenser section 120 and releases latent heat of vaporization so that heat is transferred toward the condenser section 120. The condensed liquid-phase working fluid returns to the evaporator section 110 via the groove structures 101 and begins another cycle of process. As a result, the heat pipe 10 continuously absorbs heat in the evaporator section 110 and transfers the heat to the condenser section 120 to balance temperature quickly to transfer heat.

In the embodiment, the evaporator wick 400 is disposed on the groove structures 101 in the evaporator section 110 such that the groove structures 101 provide a large surface area for vaporization for the working fluid infiltrating in the evaporator wick 400, and increases capillary force of the evaporator wick 400.

The evaporator wick 400 is made of sintered metal powder, and therefore has a very small capability radius r_(eff) which provides a strong capillary force. Meanwhile, the groove structures 101 have high permeability to reduce flow resistance of returning liquid-phase working fluid, which enables the condensed liquid-phase working fluid to quickly return to the whole evaporator section 110.

The maximum heat transfer rate Q_(max) of the heat pipe 10 in the present embodiment is increased due to the groove structures 101 in the condenser section 120. To be specific, high permeability K of the groove structures 101 increases returning speed of the condensed liquid-phase working fluid, thereby increasing the maximum heat transfer rate of the heat pipe 10.

Additionally, because there is no other structure in the condenser section 120 but the groove structures 101, the condensed liquid-phase working fluid is more capable of returning to the evaporator section 110, making the heat pipe 10 more suitable for a working condition in which the condenser section 120 is located above the evaporator section 110. On the other hand, advantages of the heat pipe 10 cannot be fully exploited when the heat pipe 10 is under antigravity working condition in which the evaporator section 110 is located above the condenser section 120, but the present invention is very suitable for zero-gravity condition or microgravity condition, such as a spacecraft.

Second Embodiment

With reference to FIGS. 4 to 6, FIG. 4 is a sectional view of the second embodiment of a heat pipe 10 a in accordance with the present invention. FIG. 5 is a sectional view of the heat pipe 10 a in FIG. 4, showing the heat pipe 10 a cut across a cutting plane line 5-5 in FIG. 4. FIG. 6 is a sectional view of the heat pipe 10 a in FIG. 4, showing the heat pipe 10 a cut across a cutting plane line 6-6 in FIG. 4.

As shown in FIGS. 4 to 6, the heat pipe 10 a has a tube 100 a, an evaporator end-cap 200 a, a condenser end-cap 300 a, an evaporator wick 400 a, and a first condenser wick 500 a. Multiple groove structures 101 a are disposed on an inner surface of the tube 100 a and uniformly arranged along a circumference of the tube 100 a.

Each one of the groove structures 101 a extends along an axial direction of the tube 100 a and extends to two opposite ends of the tube 100 a. In other words, the groove structures 101 a are disposed along the axial direction of the tube 100 a and extend transversely across the whole inner surface of the tube 100 a along a lengthwise direction of the tube 100 a. The groove structures 101 a are integrally formed in the tube 100 a.

An evaporator section 110 a and a condenser section 120 a are disposed on the tube 100. The evaporator end-cap 200 a and the condenser end-cap 300 a are each disposed at a respective one of the two opposite ends of the tube 100 a to seal the tube 100 a.

The evaporator wick 400 a is disposed in the evaporator section 110 a. The evaporator wick 400 a is made of metal powder and sintered to adhere to the groove structures 101 a. The evaporator wick 400 a is substantially uniform in thickness and uniformly adheres to the groove structures 101 a. The evaporator wick 400 a vaporizes a working fluid in the evaporator section 110 a into vapor.

The first condenser wick 500 a is disposed in the condenser section 120 a. The first condenser wick 500 a is made of metal powder and sintered to adhere to the groove structures 101 a. The first condenser wick 500 a is substantially uniform in thickness and uniformly adheres to the groove structures 101 a. The first condenser wick 500 a is connected to the evaporator wick 400 a and transfers condensed liquid-phase working fluid in the condenser section 120 a to the evaporator section 110 a. The thickness of the first condenser wick 500 a is greater than the thickness of the evaporator wick 400 a. Flow directions of working fluid vapor are indicated by dashed lines with arrows in FIG. 4. Working process of the heat pipe 10 a is explained as below with reference to FIG. 4.

The evaporator section 110 a absorbs heat from a heat source and vaporizes working fluid into vapor, resulting in localized high pressure which drives the vapor to flow toward the condenser section 120 a. The vapor condenses into liquid in the condenser section 120 a and releases latent heat of vaporization so that heat is transferred toward the condenser section 120 a. The condensed liquid-phase working fluid returns to the evaporator section 110 a via the groove structures 101 a and begins another cycle of process. As a result, the heat pipe 10 a continuously absorbs heat in the evaporator section 110 a and transfers the heat to the condenser section 120 a to balance temperature quickly to transfers heat.

In the second embodiment, the evaporator wick 400 a is disposed on the groove structures 101 a in the evaporator section 110 a such that the groove structures 101 a provide a large surface area for vaporization for the working fluid infiltrating in the evaporator wick 400 a, and increases capillary force of the evaporator wick 400 a.

The evaporator wick 400 a is made of sintered metal powder, and therefore has a very small capability radius ref, which provides a strong capillary force. Meanwhile, the groove structures 101 a have high permeability K to reduce flow resistance of returning liquid-phase working fluid, which enables the condensed liquid-phase working fluid to quickly return to the whole evaporator section 110 a.

In the second embodiment, the first condenser wick 500 a is disposed on the groove structures 101 a. The groove structures 101 a and the first condenser wick 500 a both serve as returning passages for the liquid-phase working fluid. High permeability K of the groove structures 101 a increases returning flow speed of the liquid-phase working fluid, therefore improving maximum heat transfer rate Q_(max) of the heat pipe 10 a.

Additionally, because the first condenser wick 500 a is disposed on the groove structure 101 a and the thickness of the condenser wick 500 a is greater than the thickness of the evaporator wick 400 a, when the heat pipe 10 a is under antigravity working condition in which the evaporator section 110 a is located above the condenser section 120 a, returning flow speed of the liquid-phase working fluid in the condenser section 120 a is increased, thereby increasing vaporization speed in the evaporator section 110 a. As a result, the heat pipe 10 a provides high returning flow speed and high heat transfer rate at the same time. The heat pipe 10 a of the second embodiment has more advantages under antigravity working condition in which the evaporator section 110 a is located above the condenser section 120 a.

Third Embodiment

With reference to FIGS. 7 to 10, FIG. 7 is a sectional view of the third embodiment of a heat pipe 10 b in accordance with the present invention. FIG. 8 is a sectional view of the heat pipe 10 b in FIG. 7, showing the heat pipe 10 b cut across a cutting plane line 8-8 in FIG. 7. FIG. 9 is a sectional view of the heat pipe 10 b in FIG. 4, showing the heat pipe 10 a cut across a cutting plane line 9-9 in FIG. 7. FIG. 10 is a sectional view of the heat pipe 10 b in FIG. 7, showing the heat pipe 10 b cut across a cutting plane line 11-11 in FIG. 7.

As shown in FIGS. 7 to 10, the heat pipe 10 b has a tube 100 b, an evaporator end-cap 200 b, a condenser end-cap 300 b, an evaporator wick 400 b, and a transfer wick 600 b. Multiple groove structures 101 b are disposed on an inner surface of the tube 100 b and uniformly arranged along a circumference of the tube 100 b. Each one of the groove structures 101 b extends along an axial direction of the tube 100 b and extends to two opposite ends of the tube 100 b. The groove structures 101 a are integrally formed in the tube 100 a.

An evaporator section 110 b, a transfer section 130 b, and a condenser section 120 b are sequentially disposed on the tube 100 a. The evaporator end-cap 200 b and the condenser end-cap 300 b are each disposed at a respective one of the two opposite ends of the tube 100 b to seal the tube 100 b.

The evaporator wick 400 b is disposed in the evaporator section 110 b. The evaporator wick 400 b is made of metal powder and sintered to adhere to the groove structures 101 b. The evaporator wick 400 b is substantially uniform in thickness and uniformly adheres to the groove structures 101 b. The evaporator wick 400 b vaporizes a working fluid in the evaporator section 110 b into vapor.

The transfer wick 600 b is disposed in the transfer section 130 b. The transfer wick 600 b is made of metal powder and sintered to adhere to the groove structures 101 b. The transfer wick 600 b is substantially uniform in thickness and uniformly adheres to the groove structures 101 b. The transfer wick 600 b is connected to the evaporator wick 400 b and transfers condensed liquid-phase working fluid in the transfer section 130 b to the evaporator section 110 b. The thickness of the transfer section 130 b is greater than the thickness of the evaporator wick 400 b.

Flow directions of working fluid vapor are indicated by dashed lines with arrows in FIG. 7. Working process of the heat pipe 10 b is explained as below with reference to FIG. 7.

The evaporator section 110 b absorbs heat from a heat source and vaporizes working fluid into vapor, resulting in localized high pressure which drives the vapor to flow toward the condenser section 120 b via the transfer section 130 b. The vapor condenses into liquid in the condenser section 120 b and releases latent heat of vaporization so that heat is transferred toward the condenser section 120 b. The condensed liquid-phase working fluid returns to the evaporator section 110 a via the groove structures 101 b and the transfer wick 600 b, and begins another cycle of process. As a result, the heat pipe 10 b continuously absorbs heat in the evaporator section 110 b and transfers the heat to the condenser section 120 b to balance temperature quickly to transfer heat.

In the third embodiment, the evaporator wick 400 b is disposed on the groove structures 101 b in the evaporator section 110 b such that the groove structures 101 b provide a large surface area for vaporization for the working fluid infiltrating in the evaporator wick 400 b, and increases capillary force of the evaporator wick 400 b.

The evaporator wick 400 b is made of sintered metal powder, and therefore has a very small capability radius r_(eff) which provides a strong capillary force. Meanwhile, the groove structures 101 b have high permeability K to reduce flow resistance of returning liquid-phase working fluid, which enables the condensed liquid-phase working fluid to quickly return to the whole evaporator section 110 b.

In the third embodiment, the transfer wick 600 b is disposed on the groove structures 101 b, and the groove structures 101 b extend to the condenser section 120 b. The groove structures 101 b and the transfer wick 600 b both serve as returning passages for the liquid-phase working fluid. High permeability K of the groove structures 101 b increases returning flow speed of the liquid-phase working fluid, therefore improving maximum heat transfer rate Q_(max) of the heat pipe 10 b.

Additionally, because there is no other structure in the condenser section 120 b but the groove structures 101, the condensed liquid-phase working fluid is more capable of returning to the evaporator section 110 b via the groove structures 101 and the transfer wick 600 b, making the heat pipe 10 b more suitable for a working condition in which the condenser section 120 b is located above the evaporator section 10 b. On the other hand, advantages of the heat pipe 10 b cannot be fully exploited when the heat pipe 10 b is under antigravity working condition in which the evaporator section 10 b is located above the condenser section 120 b, but the third embodiment is very suitable for zero-gravity condition such as a spacecraft.

Additionally, because the thickness of the transfer wick 600 b is greater than the thickness of the evaporator wick 400 b, returning flow speed of the liquid-phase working fluid in the condenser section 120 b is increased, thereby increasing vaporization speed in the evaporator section 10 b. As a result, the heat pipe 10 b provides high returning flow speed and high heat transfer rate at the same time.

Fourth Embodiment

With reference to FIGS. 11 to 13, FIG. 11 is a sectional view of the fourth embodiment of a heat pipe 10 c in accordance with the present invention. FIG. 12 is a sectional view of the heat pipe 10 c in FIG. 11, showing the heat pipe 10 c cut across a cutting plane line 12-12 in FIG. 11. FIG. 13 is a sectional view of the heat pipe 10 c in FIG. 11, showing the heat pipe 10 c cut across a cutting plane line 13-13 in FIG. 11.

As shown in FIGS. 11 to 13, the heat pipe 10 c has a tube 100 c, an evaporator end-cap 200 c, a condenser end-cap 300 c, an evaporator wick 400 c, and a second condenser wick 700 c. Multiple groove structures 101 c are disposed on an inner surface of the tube 100 c and uniformly arranged along a circumference of the tube 100 c. Each one of the groove structures 101 c extends along an axial direction of the tube 100 c and extends to two opposite ends of the tube 100 c. The groove structures 101 c are integrally formed in the tube 100 c.

An evaporator section 110 c and a condenser section 120 c are disposed on the tube 100 c. The evaporator end-cap 200 c and the condenser end-cap 300 c are each disposed at a respective one of the two opposite ends of the tube 100 c to seal the tube 100 c.

The evaporator wick 400 c is disposed in the evaporator section 110 c. The evaporator wick 400 c is made of metal powder and sintered to adhere to the groove structures 101 c. The evaporator wick 400 c is substantially uniform in thickness and uniformly adheres to the groove structures 101 c. The evaporator wick 400 c vaporizes a working fluid in the evaporator section 110 c into vapor.

The second condenser wick 700 c is disposed in the condenser section 120 c. The second condenser wick 700 c is made of metal powder or mesh, and is sintered to adhere to groove structures 101 c that are arranged along an upper half of the circumference of the tube 100 c. The second condenser wick 700 c has a surface that is exposed to an inner space of the tube 100 c and is planar. The second condenser wick 700 c is connected to the evaporator wick 400 c to transfer condensed working fluid in the condenser section to the evaporator section 110 c. A thickness of the second condenser wick 700 c is greater than the thickness of the evaporator wick 400 c.

Flow directions of working fluid vapor are indicated by dashed lines with arrows in FIG. 11. Working process of the heat pipe 10 c is explained as below with reference to FIG. 11.

The evaporator section 10 c absorbs heat from a heat source and vaporizes working fluid into vapor, resulting in localized high pressure which drives the vapor to flow toward the condenser section 120 c. The vapor condenses into liquid in the condenser section 120 c and releases latent heat of vaporization so that heat is transferred toward the condenser section 120 c. The condensed liquid-phase working fluid returns to the evaporator section 10 c via the groove structures 101 c and the second condenser wick 700 c, and then begins another cycle of process. As a result, the heat pipe 10 c continuously absorbs heat in the evaporator section 110 c and transfers the heat to the condenser section 120 c to balance temperature quickly to transfers heat.

In the fourth embodiment, the evaporator wick 400 c is disposed on the groove structures 101 c in the evaporator section 110 c such that the groove structures 101 c provide a large surface area for vaporization for the working fluid infiltrating in the evaporator wick 400 c, and increases capillary force of the evaporator wick 400 c.

The evaporator wick 400 c is made of sintered metal powder, and therefore has a very small capability radius r_(eff) which provides a strong capillary force. Meanwhile, the groove structures 101 c have high permeability K to reduce flow resistance of returning liquid-phase working fluid, which enables the condensed liquid-phase working fluid to quickly return to the whole evaporator section 110 c.

In the fourth embodiment, the second condenser wick 700 c is disposed on the groove structures 101 c. The groove structures 101 a and the second condenser wick 700 c both serve as returning passages for the liquid-phase working fluid. High permeability K of the groove structures 101 c increases returning flow speed of the liquid-phase working fluid, therefore improving maximum heat transfer rate Q_(max) of the heat pipe 10 c.

Additionally, because the second condenser wick 700 c is disposed on the groove structure 101 c in the condenser section 120 c, and the thickness of the second condenser wick 700 c is greater than the thickness of the evaporator wick 400 c, when the heat pipe 10 a is under antigravity working condition in which the evaporator section 110 c is located above the condenser section 120 c, returning flow speed of the liquid-phase working fluid in the condenser section 120 c is increased, thereby increasing vaporization speed in the evaporator section 110 c. As a result, the heat pipe 10 c provides high returning flow speed and high heat transfer rate at the same time. The heat pipe 10 c of the fourth embodiment has more advantages under antigravity working condition in which the evaporator section 110 c is located above the condenser section 120 c.

Fifth Embodiment

With reference to FIGS. 14 to 16, FIG. 14 is a sectional view of the fifth embodiment of a heat pipe 10 d in accordance with the present invention. FIG. 15 is a sectional view of the heat pipe 10 d in FIG. 14, showing the heat pipe 10 d cut across a cutting plane line 15-15 in FIG. 14. FIG. 16 is a sectional view of the heat pipe 10 d in FIG. 14, showing the heat pipe 10 c cut across a cutting plane line 16-16 in FIG. 14.

As shown in FIGS. 14 to 16, the heat pipe 10 d has a tube 100 d, an evaporator end-cap 200 d, a condenser end-cap 300 d, an evaporator wick 400 d, and a second condenser wick 700 c. Multiple groove structures 101 d are disposed on an inner surface of the tube 100 d and uniformly arranged along a circumference of the tube 100 d. Each one of the groove structures 101 d extends along an axial direction of the tube 100 d and extend to two opposite ends of the tube 100 d. The groove structures 101 d are integrally formed in the tube 100 d.

An evaporator section 110 d and a condenser section 120 d are disposed on the tube 100 d. The evaporator end-cap 200 d and the condenser end-cap 300 d are each disposed at a respective one of the two opposite ends of the tube 100 d to seal the tube 100 d.

The evaporator wick 400 d is disposed in the evaporator section 110 d. The evaporator wick 400 d is made of metal powder and sintered to adhere to the groove structures 101 d. The evaporator wick 400 d is substantially uniform in thickness and uniformly adheres to the groove structures 101 d. The evaporator wick 400 d vaporizes a working fluid in the evaporator section 110 d into vapor.

The second condenser wick 700 d is disposed in the condenser section 120 d and extends to the evaporator section 110 d. The second condenser wick 700 d is made of metal powder or mesh, and is sintered to adhere to groove structures 101 d that are in the condenser section 120 d and arranged along an upper half of the circumference of the tube 100 d. The second condenser wick 700 d has a surface that is exposed to an inner space of the tube 100 d and is planar. The second condenser wick 700 d is connected to the evaporator wick 400 d to transfer condensed working fluid in the condenser section to the evaporator section 110 d. A thickness of the second condenser wick 700 d is greater than the thickness of evaporator wick 400 d.

Flow directions of working fluid vapor are indicated by dashed lines with arrows in FIG. 14. Working process of the heat pipe 10 d is explained as below with reference to FIG. 14.

The evaporator section 110 d absorbs heat from a heat source and vaporizes working fluid into vapor, resulting in localized high pressure which drives the vapor to flow toward the condenser section 120 d. The vapor condenses into liquid in the condenser section 120 d and releases latent heat of vaporization so that heat is transferred toward the condenser section 120 d. The condensed liquid-phase working fluid returns to the evaporator section 110 d via the groove structures 101 d and the second condenser wick 700 d, and then begins another cycle of process. As a result, the heat pipe 10 d continuously absorbs heat in the evaporator section 110 d and transfers the heat to the condenser section 120 d to balance temperature quickly to transfer heat.

In the fifth embodiment, the evaporator wick 400 d is disposed on the groove structures 101 d in the evaporator section 110 d, and the second condenser wick 700 d adheres to the groove structures 101 d that are arranged along an upper half of the circumference of the tube 100 d. As a result, the groove structures 101 d provide a large surface area for vaporization for the working fluid infiltrating in the evaporator wick 400 d and the second condenser wick 700 d located in the evaporator section 110 d, and therefore increases capillary force of the evaporator wick 400 d and the second condenser wick 700 d located in the evaporator section 110 d.

The evaporator wick 400 d and the second condenser wick 700 d are made of sintered metal powder, and therefore have a very small capability radius r_(eff) which provides a strong capillary force. Meanwhile, the groove structures 101 d have high permeability K to reduce flow resistance of returning liquid-phase working fluid, which enables the condensed liquid-phase working fluid to quickly return to the whole evaporator section 110 d.

In the fifth embodiment, the second condenser wick 700 d is disposed on the groove structures 101 d. The groove structures 101 d and the second condenser wick 700 d both serve as returning passages for the liquid-phase working fluid. High permeability K of the groove structures 101 d increases returning flow speed of the liquid-phase working fluid, therefore improving maximum heat transfer rate Q_(max) of the heat pipe 10 d.

Additionally, because the second condenser wick 700 d is disposed on the groove structure 101 d in the condenser section 120 d, and the thickness of the second condenser wick 700 d is greater than the thickness of the evaporator wick 400 d, when the heat pipe 10 d is under antigravity working condition in which the evaporator section 110 d is located above the condenser section 120 d, returning flow speed of the liquid-phase working fluid in the condenser section 120 d is increased, thereby increasing vaporization speed in the evaporator section 110 d. As a result, the heat pipe 10 d provides high returning flow speed and high heat transfer rate at the same time. The heat pipe 10 d of the fifth embodiment has more advantages under antigravity working condition in which the evaporator section 110 d is located above the condenser section 120 d.

More about the Aforementioned Embodiments

(1) The tube of the heat pipe is made of heat conductive materials such as copper, aluminum, carbon steel, stainless steel, alloy steel, gold, or silver. The working fluid is a heat conductive medium such as water, acetone, or ammonia, depending on the need for heat transfer.

The evaporator section of the tube is used to thermally couple to the heat source (not shown in figures), such as a central processing unit or a graphics processing unit, to absorb heat generated thereby. The condenser section of the tube is used to thermally couple to the cooling fins (not shown in figures) to dissipate the heat generated by the heat source.

(2) In the second, fourth and fifth embodiments, because a condenser wick (the first condenser wick or the second condenser wick) is disposed in the condenser section, and a thickness of the condenser wick is greater than the thickness of the evaporator wick, when the heat pipe 10 d is under antigravity working condition in which the evaporator section 110 d is located above the condenser section 120 d, returning flow speed of the liquid-phase working fluid in the condenser section 120 d is increased, thereby increasing vaporization speed in the evaporator section 110 d. As a result, the heat pipe 10 d provides high returning flow speed and high heat transfer rate at the same time.

The condenser section in the first and third embodiments is more suitable for zero-gravity condition and for the working condition in which the condenser section is located above the evaporator section. The returning flow speed of the liquid-phase working fluid is sufficiently high when a length of the condenser section is less than or equal to 200 mm due to larger permeability K of the groove structures. When the length of the condenser section is greater than 200 mm, the condenser section may have a problem with returning flow when there are only groove structures in the condenser section. Therefore, a wick, such as the condenser wick in the second, fourth, and fifth embodiments, has to be disposed on the groove structures to improve the returning flow speed of the condensed liquid-phase working fluid when the length of the condenser section is greater than 200 mm.

(3) A shape of a cross section of the tube is round in the first embodiment through the fifth embodiment, but the shape of the tube is not limited thereto. In another preferred embodiment, the shape of a cross section of the tube is selected from the group consisting of circle, oval, rectangle, flattened racetrack, and polygon having more than four sides.

(4) The tube in the first embodiment through the fifth embodiment has, but not limited to, a fixed cross-section. In another preferred embodiment, the tube has a variable cross-section or the tube is a corrugated pipe.

(5) The tube in the first embodiment through the fifth embodiment is a straight tube, meaning the evaporator section, the transfer section and the condenser section are parallel to each other, but the tube is not limited thereto. In another preferred embodiment, the tube can be a curved tube, meaning the evaporator section, the transfer section, and the condenser section are not parallel to each other.

(6) A shape of a cross section of each one of the groove structures in the first embodiment through the fifth embodiment is, but not limited to, triangular. In another preferred embodiment, the shape of the cross section of each one of the groove structures can be either rectangular or trapezoidal depending on the need.

(7) The wicks in the first embodiment through the fifth embodiment are preferably made of copper.

In summary, the present invention provides the heat pipe having groove structures formed in the inner surface of the tube and disposed in the evaporator section to provide a large surface area for vaporization for the working fluid infiltrating in the evaporator wick and increases capillary force of the evaporator wick. The second condenser wick is made of metal powder or mesh, and therefore has a very small capability radius r_(eff) which provides a strong capillary force. The groove structures have high permeability K to reduce flow resistance of returning liquid-phase working fluid, which enables the condensed liquid-phase working fluid to quickly return to the whole evaporator section. The present invention has a high capillary force and a high permeability K at the same time to improve heat transfer rate of the heat pipe, solving a dilemma of the conventional single type capillary structure. The present invention has good manufacturing process repeatability and is reliable, easy to manufacture, and low-cost.

Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and features of the invention, the disclosure is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

What is claimed is:
 1. A heat pipe comprising: a tube having multiple groove structures disposed on an inner surface of the tube and arranged along a circumference of the tube; each one of the groove structures extending along an axial direction of the tube and extending to two opposite ends of the tube; an evaporator section; and a condenser section; two end-caps; each one of the two end-caps disposed at a respective one of the two opposite ends of the tube; the two end-caps sealing the tube; and an evaporator wick disposed in the evaporator section, the evaporator wick made of metal powder and sintered to adhere to the groove structures; the evaporator wick being uniform in thickness and uniformly adhering to the groove structures; the evaporator wick vaporizing a working fluid in the evaporator section.
 2. The heat pipe as claimed in claim 1, wherein the groove structures are evenly arranged along the circumference of the tube.
 3. The heat pipe as claimed in claim 1, wherein the groove structures are integrally formed in the tube.
 4. The heat pipe as claimed in claim 2, wherein the groove structures are integrally formed in the tube.
 5. The heat pipe as claimed in claim 1, wherein the heat pipe comprises a first condenser wick disposed in the condenser section; the first condenser wick made of metal powder and sintered to adhere to the groove structures; the first condenser wick being uniform in thickness and uniformly adhering to the groove structures; the first condenser wick connected to the evaporator wick, the first condenser wick transferring condensed working fluid in the condenser section to the evaporator section via the evaporator wick.
 6. The heat pipe as claimed in claim 1, wherein the heat pipe comprises a first condenser wick disposed in the condenser section; the first condenser wick made of metal powder and sintered to adhere to the groove structures; the first condenser wick being uniform in thickness and uniformly adhering to the groove structures; the first condenser wick connected to the evaporator wick, the first condenser wick transferring condensed working fluid in the condenser section to the evaporator section via the evaporator wick.
 7. The heat pipe as claimed in claim 5, wherein a thickness of the first condenser wick is greater than a thickness of the evaporator wick.
 8. The heat pipe as claimed in claim 6, wherein a thickness of the first condenser wick is greater than a thickness of the evaporator wick.
 9. The heat pipe as claimed in claim 1, wherein the heat pipe has a transfer section disposed between the evaporator section and the condenser section; and a transfer wick disposed in the transfer section; the transfer wick made of metal powder and sintered to adhere to the groove structures; the transfer wick being uniform in thickness and uniformly adhering to the groove structures; the transfer wick connected to the evaporator wick, the transfer wick transferring condensed working fluid in the transfer section to the evaporator section.
 10. The heat pipe as claimed in claim 2, wherein the heat pipe has a transfer section disposed between the evaporator section and the condenser section; and a transfer wick disposed in the transfer section; the transfer wick made of metal powder and sintered to adhere to the groove structures; the transfer wick being uniform in thickness and uniformly adhering to the groove structures; the transfer wick connected to the evaporator wick, the transfer wick transferring condensed working fluid in the transfer section to the evaporator section.
 11. The heat pipe as claimed in claim 9, wherein the thickness of the transfer wick is greater than the thickness of the evaporator wick.
 12. The heat pipe as claimed in claim 10, wherein the thickness of the transfer wick is greater than the thickness of the evaporator wick.
 13. The heat pipe as claimed in claim 1, wherein the tube extends transversely; the heat pipe comprises a second condenser wick disposed in the condenser section, the second condenser wick made of metal powder or mesh and sintered to adhere to the groove structures that are arranged along an upper half of the circumference of the tube, the second condenser wick having a surface exposed to an inner space of the tube and being planar, the second condenser wick connected to the evaporator wick, and the second condenser wick transferring condensed working fluid in the condenser section to the evaporator section.
 14. The heat pipe as claimed in claim 1, wherein the tube extends transversely; the heat pipe comprises a second condenser wick disposed in the condenser section, the second condenser wick made of metal powder or mesh and sintered to adhere to the groove structures that are arranged along an upper half of the circumference of the tube, the second condenser wick having a surface exposed to an inner space of the tube and being planar, the second condenser wick connected to the evaporator wick, and the second condenser wick transferring condensed working fluid in the condenser section to the evaporator section.
 15. The heat pipe as claimed in claim 13, wherein a thickness of the second condenser wick is greater than a thickness of the evaporator wick.
 16. The heat pipe as claimed in claim 14, wherein a thickness of the second condenser wick is greater than a thickness of the evaporator wick.
 17. The heat pipe as claimed in claim 15, wherein the second condenser wick extends to the evaporator section, and the second condenser wick adheres to the evaporator wick that is disposed on the upper half of the circumference of the tube.
 18. The heat pipe as claimed in claim 16, wherein the second condenser wick extends to the evaporator section, and the second condenser wick adheres to the evaporator wick that is disposed on the upper half of the circumference of the tube.
 19. The heat pipe as claimed in claim 1, wherein a shape of a cross section of each one of the groove structures is triangular.
 20. The heat pipe as claimed in claim 2, wherein a shape of a cross section of each one of the groove structures is triangular.
 21. A heat pipe comprising: a tube having multiple groove structures disposed on an inner surface of the tube and arranged along a circumference of the tube; each one of the groove structures extending along an axial direction of the tube and extending to two opposite ends of the tube, and the groove structures reducing flow resistance of liquid phase working fluid; an evaporator section; and a condenser section; and an evaporator wick disposed in the evaporator section and adhering to the groove structures, and the evaporator wick vaporizing a working fluid in the evaporator section.
 22. The heat pipe as claimed in claim 21, wherein the groove structures are evenly arranged along the circumference of the tube. 